Equipment Technology CEC


Published on

Published in: Business, Technology
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Equipment Technology CEC

  1. 2. Course Objectives <ul><li>Understand how pressure transducers and respiratory inductance plethysmography belts work </li></ul><ul><li>Know why these types of technology are used to measure nasal pressure and respiratory effort in the sleep lab </li></ul><ul><li>Use these types of equipment to collect the best quality signals possible </li></ul>
  2. 3. Pressure Transduction <ul><li>Transduction : the converting of energy from one form to another </li></ul><ul><ul><li>e.g., pressure (mechanical energy) to electrical energy </li></ul></ul>
  3. 4. Previous/Alternative Methods of Measuring Airflow <ul><li>A pneumotachograph is the most accurate way of measuring airflow </li></ul><ul><li>Consists of a measuring </li></ul><ul><li>device placed inside a </li></ul><ul><li>full-face mask </li></ul><ul><li>All the air a patient </li></ul><ul><li>breathes must go through </li></ul><ul><li>the device </li></ul><ul><li>Can be uncomfortable </li></ul><ul><li>for the patient </li></ul>
  4. 5. <ul><li>Thermal-based flow sensors are still used in conjunction with pressure transducers </li></ul><ul><ul><li>Thermocouples are made of two dissimilar metals and detect the rate of temperature change of exhaled air </li></ul></ul><ul><ul><li>Thermistors use changes in conductivity to detect changes in temperature between room air and exhaled air </li></ul></ul>Previous/Alternative Methods of Measuring Airflow
  5. 6. <ul><li>Thermal-based flow devices routinely under-detect respiratory events by up to 70% </li></ul><ul><li>Flow tracing can be inaccurate if the room is very warm or if a fan or space heater is on </li></ul><ul><li>If used with PAP titrations, air flowing through the mask can dilute patient’s airflow and make signal useless </li></ul>Previous/Alternative Methods of Measuring Airflow
  6. 7. How Pressure Transducers Work <ul><li>Pressure sensing devices are becoming the standard for measuring airflow </li></ul><ul><li>They use a nasal cannula connected to a sensitive pressure transducer, which measure actual volume of exhaled air </li></ul>
  7. 8. <ul><li>The transducer turns pressure input into an electrical signal </li></ul><ul><ul><li>That signal is sent to an amplifier with a corresponding voltage and translated on the study as a flow volume tracing </li></ul></ul><ul><li>Pressure transducers provide what is considered to be one of the most accurate measurements of flow volume available </li></ul>How Pressure Transducers Work
  8. 9. Why They’re Used <ul><li>Produce a signal very comparable to a pneumotachograph, while being much more comfortable for the patient </li></ul><ul><li>Are qualitative devices which require no periodic calibration </li></ul><ul><li>Allow for much more accurate detection of RERAs and flow limitations </li></ul>
  9. 10. Technical Considerations <ul><li>Using unfiltered output, the tracing will show: </li></ul><ul><ul><li>A flattening of the waveform when snoring </li></ul></ul><ul><ul><li>A series of fast, high frequency waveforms </li></ul></ul><ul><li>Using filtered output, a 2.5 Hz high frequency filter will filter out snoring </li></ul><ul><ul><li>Only a flattening of the waveform will be seen </li></ul></ul>
  10. 12. Technical Considerations <ul><li>If available on your particular device, the gain set button can be pressed to automatically optimize the transducer’s output level </li></ul><ul><li>AASM recommended settings for nasal pressure: </li></ul><ul><ul><li>Sampling rate of 100 Hz </li></ul></ul><ul><ul><li>Low frequency filter of 0.1 Hz </li></ul></ul><ul><ul><li>High frequency filter of 15 Hz </li></ul></ul>
  11. 14. Troubleshooting <ul><li>If you have a complete loss of signal: </li></ul><ul><ul><li>Check if cannula prongs are coming out of nares – may need to secure with tape </li></ul></ul><ul><ul><li>Make sure prongs are neither too long nor trimmed too short </li></ul></ul><ul><ul><li>If a patient has a cold or severe rhinorrhea, the nasal cannula may become completely blocked with mucus </li></ul></ul><ul><li>If the signal seems chaotic: </li></ul><ul><ul><li>Check the filter settings </li></ul></ul>
  12. 15. Troubleshooting <ul><li>Recommended order for troubleshooting a poor flow signal: </li></ul><ul><ul><li>1) Ensure cannula is properly positioned </li></ul></ul><ul><ul><li>2) Check all transducer connections to the headbox </li></ul></ul><ul><ul><li>3) Verify proper input selections </li></ul></ul><ul><ul><li>4) Make sure batteries are fresh </li></ul></ul><ul><ul><li>5) Check for plugged cannula tips </li></ul></ul><ul><ul><li>6) Confirm sensitivity, filter settings, and sampling rates </li></ul></ul>
  13. 16. Inductance Plethysmography <ul><li>Plethysmography is the measuring and recording of changes in volume of a body part or organ </li></ul><ul><li>In terms of sleep applications, the measurement is of the change in lung and abdominal volume during respiration </li></ul><ul><ul><li>The main reason we measure respiratory effort is to differentiate between OSAs and CSAs, but inductance plethysmography is also useful for detecting flow limitations and paradoxical breathing </li></ul></ul>
  14. 17. Previous/Alternative Methods of Measuring Respiratory Effort <ul><li>The gold standard of respiratory effort measurement is esophageal manometry </li></ul><ul><ul><li>Detects pressure changes in the esophagus, which correlate to the amount of strain in the airway during respiration </li></ul></ul>
  15. 18. <ul><li>Esophageal manometry (continued) </li></ul><ul><ul><li>A catheter is either fed through the nose by the technician or swallowed by the patient, and it resides in the lower esophagus throughout the study </li></ul></ul><ul><ul><li>Measures thoracic effort directly, and offers the best “proof” of OSA </li></ul></ul><ul><ul><li>Not practical as patients are often intolerant </li></ul></ul>Previous/Alternative Methods of Measuring Respiratory Effort
  16. 19. <ul><li>Two other types of plethysmography have been used: </li></ul><ul><li>Elastometric plethysmography uses piezo-electric sensors, which utilize silicone crystals that produce electrical signals when put through mechanical stress </li></ul><ul><ul><li>Provides a qualitative, rather than quantitative, measure of respiratory effort </li></ul></ul><ul><ul><li>Is subject to “trapping” artifact </li></ul></ul>Previous/Alternative Methods of Measuring Respiratory Effort
  17. 20. <ul><li>Elastometric plethysmography (cont.) </li></ul><ul><ul><li>Can significantly under- and/or overestimate actual degree of movement </li></ul></ul><ul><ul><li>Creates a false signal with change in body position </li></ul></ul><ul><ul><li>Can cause “false paradoxing” </li></ul></ul><ul><ul><ul><li>Due to the nature of the piezo crystals, polarity may spontaneously flip </li></ul></ul></ul><ul><ul><ul><li>Belts may show paradoxical breathing when it isn’t actually occurring </li></ul></ul></ul>Previous/Alternative Methods of Measuring Respiratory Effort
  18. 21. <ul><li>Impedance plethysmography uses the electrical impedance of the body to measure respiratory effort </li></ul><ul><ul><li>A weak current is passed through 2 to 4 electrodes that are attached to the body </li></ul></ul><ul><ul><li>The amount of impedance changes with changing lung volume, and is measured to yield a representation of respiratory effort </li></ul></ul><ul><ul><li>Rarely used due to risk involved when running a current through a patient’s body </li></ul></ul><ul><ul><li>Frequency generated may interfere with other monitoring equipment or pacemakers </li></ul></ul>Previous/Alternative Methods of Measuring Respiratory Effort
  19. 22. How Respiratory Inductance Plethysmography Works <ul><li>Gives a semi-quantitative reading of respiratory effort, making it possible to accurately record true paradoxical breathing </li></ul><ul><li>Relies on two principles of physics, Faraday’s law and Lenz’s law . </li></ul>
  20. 23. <ul><li>Faraday’s law </li></ul><ul><ul><li>States that a current applied through a loop of wire generates a magnetic field at a 90 degree angle to the loop </li></ul></ul><ul><li>Lenz’s law </li></ul><ul><ul><li>States that a change in the area enclosed in the loop creates an opposing current within the loop, directly proportional to the change in the area </li></ul></ul>How Respiratory Inductance Plethysmography Works
  21. 24. <ul><li>A shielded coiled wire is sewn into an elastic belt to allow for expansion and contraction: </li></ul><ul><li>A small electrical current is passed through the wire, creating a magnetic field </li></ul>How Respiratory Inductance Plethysmography Works
  22. 25. <ul><li>The act of breathing changes the cross-sectional area of the body, changing the shape of the magnetic field </li></ul><ul><ul><li>This induces an opposing current (Lenz’s law), which is measured as a change in frequency of the applied current </li></ul></ul>How Respiratory Inductance Plethysmography Works
  23. 26. <ul><li>The signals generated </li></ul><ul><li>are sent through </li></ul><ul><li>frequency oscillators, </li></ul><ul><li>which are then distributed to a demodulator device </li></ul><ul><li>The demodulator then converts the signals into analogue form for recording of respiratory effort </li></ul>How Respiratory Inductance Plethysmography Works
  24. 27. Why It’s Used <ul><li>Signal produced is linear, and is a fairly accurate representation of change in cross-sectional area </li></ul><ul><li>No current passes through the patient’s body </li></ul><ul><li>Does NOT rely on belt tension, so isn’t subject to trapping artifact or false paradoxing </li></ul>
  25. 28. Why It’s Used <ul><li>Can much more accurately detect paradoxical breathing </li></ul><ul><ul><li>Some RIP driver modules include a “sum” channel that provides a true indication of paradoxical breathing </li></ul></ul><ul><ul><li>When the chest and abdomen are moving synchronously, the sum channel will show a sine wave pattern </li></ul></ul><ul><ul><li>The more out of sync a patient is breathing, the flatter the sum channel will be. </li></ul></ul>
  26. 30. Why It’s Used <ul><li>According to the AASM, “the sensor for detection of respiratory effort is either esophageal manometry, or calibrated or uncalibrated inductance plethysmography.” </li></ul><ul><li>Since manometry isn’t a viable option in the sleep lab setting, RIP is usually the method of choice for measuring respiratory effort. </li></ul>
  27. 31. Technical Considerations <ul><li>AASM recommended settings for inductance plethysmography: </li></ul><ul><ul><li>Sampling rate of 100 Hz </li></ul></ul><ul><ul><li>Low frequency filter of 0.1 Hz </li></ul></ul><ul><ul><li>High frequency filter of 15 Hz </li></ul></ul><ul><li>Do NOT clean belts with alcohol or alcohol-based products! </li></ul><ul><ul><li>Alcohol can degrade the wire coating and cause it to break </li></ul></ul><ul><ul><li>Clean with warm water and detergent </li></ul></ul><ul><ul><li>Most RIP belts are machine washable </li></ul></ul>
  28. 32. Troubleshooting <ul><li>If the belt is too loose, no signal will be generated </li></ul><ul><ul><li>Also, if belts are too loose, they may overlap each other and cause conflicting magnetic fields </li></ul></ul><ul><li>Unlike piezo belts, you need to be extra careful not to overtighten RIP belts </li></ul><ul><ul><li>If they’re too tight, they can actually restrict chest and abdominal movement </li></ul></ul><ul><ul><li>When putting belts on a patient, unstretched the ends should come 5-6” from touching </li></ul></ul>
  29. 33. Troubleshooting <ul><li>Most common cause of poor readings is incorrect placement </li></ul><ul><ul><li>Chest belt should be just above the nipple line </li></ul></ul><ul><ul><li>Abdominal belt should be just above the belly button </li></ul></ul><ul><ul><li>Some patients’ body shapes can cause belts to ride up or down </li></ul></ul><ul><ul><ul><li>Belts can be taped to patients’ clothing if needed </li></ul></ul></ul><ul><ul><li>For patients with limited chest wall movement of shallow breathing, all you can really do is increase the gain </li></ul></ul>
  30. 34. Troubleshooting <ul><li>Make sure belts are dry </li></ul><ul><ul><li>Wet belts can cause high-frequency artifact </li></ul></ul><ul><li>RIP belts, unlike piezos, should not need to be adjusted when a patient changes position since they are not subject to trapping artifact </li></ul><ul><ul><li>If signal amplitude decreases, you should only need to increase the gain </li></ul></ul><ul><li>It’s normal for the signal amplitude to decrease when the patient falls asleep and begins breathing more shallowly </li></ul>
  31. 35. Troubleshooting <ul><li>If the wire in the belt has broken, you will see no signal at all (not just a low-amplitude signal) </li></ul><ul><li>When in doubt, change the batteries </li></ul><ul><ul><li>When the batteries are going bad, you usually won’t see a complete loss of signal, but may see artifact or a “choppy” reading </li></ul></ul>
  32. 36. Some Notes About RERAs <ul><li>Pressure transduction and inductance plethysmography were adopted by the AASM mainly because of how much more accurately they allow for the detection of RERAs </li></ul>
  33. 37. Some Notes About RERAs <ul><li>According to the AASM: </li></ul><ul><ul><li>A RERA is “a sequency of breaths lasting at least 10 seconds characterized by increasing respiratory effort or flattening of the nasal pressure waveform leading to an arousal from sleep when the sequence of breaths does not meet the criteria for an apnea of hypopnea.” </li></ul></ul><ul><ul><li>“ With respect to scoring a RERA, use of esophageal pressure is the preferred method of assessing change in respiratory effort, although nasal pressure and inductance plethysmography can be used.” </li></ul></ul>
  34. 38. Some Notes About RERAs <ul><li>On a pressure transducer’s waveform, normal breathing appears as a series of sinusoidal waveforms </li></ul><ul><li>During inhalation, the airway becomes unstable and will not let airflow through </li></ul><ul><ul><li>This results in a flattening of the nasal pressure waveform, and increase in the inspiratory phase, and a decrease in the amplitude of the waveform </li></ul></ul>
  35. 39. Some Notes About RERAs <ul><li>Flow limitation is the hallmark of RERAs </li></ul><ul><li>Pressure transducers and RIP belts demonstrate flow limitation by a “squaring off” of the waveform </li></ul>
  36. 40. Some Notes About RERAs <ul><li>During periods of partial airway collapse, you’ll see a characteristic plateau to the waveform </li></ul>
  37. 41. Some Notes About RERAs <ul><li>Sustained flow limitations without arousals are also seen as a “squaring off,” and this is particularly common in SWS </li></ul><ul><li>Pressure transducers have been shown to be as effective as esophageal manometry at detecting flow-limitation events like RERAs, but they’re much better tolerated by patients </li></ul>
  38. 42. Some Notes About RERAs <ul><li>With a thermal sensor alone, snoring may be the only indicator that partial obstruction is present </li></ul><ul><li>Norman et al. demonstrated in 1997 that transducers are much more sensitive to picking up RERAs </li></ul><ul><ul><li>61.4% of RERAs seen with a transducer were completely missed by a thermistor </li></ul></ul>
  39. 43. The transducer signal indicates a true flow limitation prior to an arousal and verifies that the arousal is clearly associated with respiration
  40. 44. Some Notes About RERAs <ul><li>Inductance plethysmography is helpful in detecting RERAs as well </li></ul><ul><li>RERAs are often characterized by crescendo patterns in intrathoracic pressure immediately prior to an arousal </li></ul>
  41. 46. <ul><li>Now for some example screenshots! </li></ul>
  42. 47. What happened with this pressure flow signal?
  43. 48. What phenomenon is taking place here in the nasal pressure signal?
  44. 49. Is this chest and abdominal belt activity an equipment malfunction that needs to be fixed or a result of the patient’s breathing pattern?
  45. 50. What’s going on with these belts? (These screen shots are from different times in the same study)
  46. 51. Is there something wrong with this chest belt, or is this an accurate reading?
  47. 52. Conclusion <ul><li>Nasal cannula pressure transduction and respiratory inductance plethysmography are adapted approximations of their respective gold standards </li></ul><ul><li>They were designed to be more comfortable for the patient, and are used because they’ve been shown to be just as reliable </li></ul><ul><li>Overall, a nasal pressure sensor and effort belts using RIP technology are extremely helpful when scoring airflow events, especially if the event is ambiguous </li></ul>
  48. 53. Questions, Concerns, Feedback Should you have any questions or feedback regarding this presentation please feel free to contact our program director, Jennifer Brickner-York, at [email_address] . Thank You.
  49. 54. References <ul><li>Ayappa, I., Norman, R.G., Krieger, A.C., Rosen, A., O'Malley, R.L., & Rapoport, D.M. (2000). Non-invasive detection of respiratory event-related arousals (RERAs) by a nasal cannula/pressure transducer system. Sleep , 23 (6), 763-66. </li></ul><ul><li>Iber, C., Ancoli-Israel, S., Chesson, A.L., Quan, S.F. (2007). The AASM manual for the scoring of sleep and associated events. Westchester, IL: American Academy of Sleep Medicine. </li></ul><ul><li>Loube, D.I., Andrada, T., & Howard, R.S. (1999). Accuracy of respiratory inductive plethysmography for the diagnosis of upper airway resistance syndrome. Chest, 115(5), 1333-37. </li></ul><ul><li>Mazeika, G.G., & Swanson, R. (2007). Respiratory inductance plethysmography: an introduction. Mukilteo, WA: Pro-Tech Services. </li></ul><ul><li>Norman, R.G., Ahmed, M.M., Walsleben, J.A., & Rapoport, D.M. (1997). Detection of respiratory events during NPSG: nasal cannula/pressure transducer sensor versus thermistor [abstract]. Sleep, 20(12), 1175-84. </li></ul><ul><li>Philips Healthcare. (2009). Pro-Tech sensors usage guide and FAQs. </li></ul><ul><li>Respironics Medical Education Department. (2008). Introduction to diagnostic equipment for the sleep technologist. </li></ul><ul><li>Spriggs, W.H. (2008). Essentials of polysomnography . Boston, MA: Sleep Ed, LLC. </li></ul>